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  • #31
    Re: Classic Pressure?

    WOW.... what a great thread this is evolving into....this is what I love about this forum... I come along with a question hoping to get an answer, and get some great responses and am then able to add my experiences into the mix for others to try the same mod. The result is we all learn, and we all heap eachother make better espresso!!

    What a great forum - thankyou to all!

    Ben

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    • #32
      Re: Classic Pressure?

      I have a Classic but the pump seems to be different to those mentioned. It is an Invensys cp3a/ST 65w 230V. I cant find a flow/pressure diagram for it. How would I know if the OPV is set correctly? Currently Im getting 100ml in 30sec using the test method described here.

      Thanks
      Ken

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      • #33
        Re: Classic Pressure?

        Gday Ken,
        have a look at this link and then click on the schematic part and it will give you a flow rate chart for your pump.
        http://tinyurl.com/eos5j
        Hope this helps.

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        • #34
          Re: Classic Pressure?

          Thanks Lovey

          tinyurl seems to be down so Ill check later

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          • #35
            Re: Classic Pressure?

            From the diagram it looks as though Im at c.10bar so Ill probably try and get to 125ml and see if things get better.
            Thanks

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            • #36
              Re: Classic Pressure?

              Success. Got 120ml second try. Decided to leave it there for the moment. I can now get a 25s shot and taste seems much smoother with a darker, thicker crema.

              Thanks

              Comment


              • #37
                Re: Classic Pressure?

                Sparky has nailed it (as usual). The proper OPV for non-solenoid Gaggias is the T-piece on the end of the Ulka pump (part 43 in the exploded Espresso diagram). According to some alties, this should be readily adjustable with a screwdriver but with one that I tried from a broken Evolution, the screw head started stripping before it turned - I havent tried on my beloved Carezza yet but i know that it never seems to operate.

                AndyCJ has circled in red the T-junction on part 26 which is the stupid "anti-drip system" valve that all non-solenoid Gaggias (except Grans, apparently) are afflicted with. These act as both a secondary OPV and also as a boiler draning device for when the machine is idle at brew setting (you can hear them gurgle periodically as a bit of steam leaks past). The interior hides a little rubber ball which plugs that return pipe and is pretty much unadjustable as well as being worse than useless (since it allows the boiler to dry out when left for extended idle periods). If I get around to adjusting the pump OPV on my Carezza, I will block this fitting off but right now it acts as a bad OPV - bad as excess pressure is bled out through the hottest part of the boiler rather than before cool water enters which should do wonders for temp instability.

                Dilbert3000 has correctly marked the OPV on solenoid model Gaggias (except for ancient Coffees which had them coming off another group fitting which cools the group by allowing excess cool water to pump through).

                I hope my belated response is of some use.

                Greg

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                • #38
                  Re: Classic Pressure?

                  My feeling was that the ball valve at the top of the boiler on my old Espresso had 2 main consequences:

                  1) If the boiler was partially full the ball dropped uncovering the outlet tube. When the pump was switched on water level rose until the ball reached the level of the outlet, was pushed against the hole, sealed it and allowed pressure to build in the boiler. It allowed any air to be vented from the boiler without manually opening the steam valve. Water level or steam pressure kept the ball in the outlet sealing the boiler. I think this is its main function. I dont think it has an overpressure relief function.

                  2) As waterlevel falls the ball drops away from the outlet letting air into the boiler. I live in a very hard water area. If the spring valve at the bottom of the boiler had any scale in it the boiler drained aided by the air entering from the top. If there is any scale on the ball valve it never seats properly and water will flow out into the tank when the pump is on and never reaches pressure.

                  The absence of this valve is the biggest benefit I have seen moving to a Classic. It makes me glad I was hamfisted enough to kill the Espresso!

                  Ken

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                  • #39
                    Re: Classic Pressure?

                    If you choke a non-solenoid Gaggia, then youll get water flowing out of the ball valve and if you leave one idle for about an hour, you can hear steam gurgle through the water tank from the return hose.

                    What you describe in 1) is possibly the intended function but then why not have it on the solenoid machines as well (assuming it worked)?

                    Greg

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                    • #40
                      Re: Classic Pressure?

                      These 2 links show the different steam valve assemblies:

                      https://www.shop.partsguru.com/displayProductDocument.hg?productId=466&categoryId =32

                      https://www.shop.partsguru.com/displayProductDocument.hg?productId=334&categoryId =79

                      One without the ball valve and the other with, describing it as a self-priming valve.

                      The Partsguru exploded diagram for the Espresso doesnt show the ball valve. The Coffee diagram shows drains to the tank from both the high pressure relief valve attached to the pump and the ball valve.

                      I suppose if the ball valve deforms under pressure it could act as an OPV otherwise the pressure would just improve the seal.

                      That the solendoid machines dont have the valve suggests that with the solendoid (and without the spring valve in the base of the boiler) some function it performs isnt needed.

                      Perhaps with the better seal from the solenoid the need to prime is greatly reduced.

                      With both machines brew water is taken from the top of the boiler. With the solenoid, air goes out via the brew head easily and the boiler more or less fills. The spring valve in the non-solenoid machines could maintain a significant pressure in the boiler against the pump regardless of whether there is a puck. If the boiler is full of air, pressurised and fails it would be much more dangerous than one filled with water. Perhaps it is a safety device to prevent this situation.

                      My problem with scale is why Im happier with the Classic. The Espresso still made good coffee.

                      Ken

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                      • #41
                        Re: Classic Pressure?

                        Help... Im a complete newbie :, and I wouldnt know where to start... Im attaching a picture, would someone be as kind as to point me in the right direction, I would be eternally grateful... thankyou

                        Comment


                        • #42
                          Re: Classic Pressure?

                          Hi Guys

                          I have been looking around the site for a while now and there is a lot of great info here. It sounds like the mod to the gaggia classic is well worth while and would like to do it on my own machine but there seems to be a problem. As in the picture in the above post, my gaggia has a clear silicon tube that returns to the water reservior and not the black tube shown in other photos. My problem seems to be that with this model (not sure if its newer or older then the ones that have had the mod successfully done on them) the hex nut isnt actually removable. When the silicon tube is removed and looking into the valve there isnt any sign of an adjustable part (only a small hole at the base of a void in the brass).

                          Any ides as to if this model of the classic can have the OPV mod done to it would be accperciated.

                          Cheers Iain

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                          • #43
                            Re: Classic Pressure?

                            The picture posted by DomCoff above is exactly the type of classic that can be adjusted. The OPV adjustment is hidden underneath the nut that the return silicone tube exits from. You can see it in the picture.

                            If I understand you correctly, youve taken the brass barb off (the brass cap with the nipple that the silicone tube is attached to) to reveal what looks to be a void with a hole in it. From memory, that hole isnt a hole, but a hex socket that takes a 5 mm allen key. It looks like a hole when there is water in it, but if you dry it with a paper towel, youll see it is a socket. You have to rotate it anti-clockwise about 270 degrees (in my case) maybe more, depending on your initial setting. The details are more fully described in the first part of the thread.

                            I hope that helps.

                            Cheers,

                            Mark.

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                            • #44
                              Re: Classic Pressure?

                              Just to make sure, What I should be unscrewing is the brass connection labeled 4 on my included pic?
                              Thanks
                              Dom

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                              • #45
                                Re: Classic Pressure?

                                I hope you mean 3. Its the one in the large yellow circle. There is no need to remove anything else.

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